(1) Field of the Invention
This invention relates generally to digital photography and relates more specifically to image stabilization system and methods to compensate for any movements as e.g. hand tremor when a photo is taken and an apparatus using the same.
(2) Description of the Prior Art
Image stabilization techniques or anti-shake technologies are employed in critical sceneries to reduce the effects of camera movements during image capture or to enable to prolong a maximum possible exposure time in digital photography. Typical usage scenarios are e.g. low light scenarios without a tripod with long exposure times required, environments with strong intrinsic movements (e.g. boats), image capture using telephoto lenses, or video applications.
It has to be noted that ergonomics of a camera influences in a vast extent the user's ability to make non-blurred images. Cameras built-in mobile phones or miniature cameras suffer from shaking more than normal-size cameras.
For typical applications in non-moving environments physiological tremor contributes mostly to hand shaking. Physiological tremor is present with all human beings, albeit it is also highly dependent upon the actual condition of an individual photographer. Typical amplitude of a physiological tremor is in the order of 0.5 to 1 degree. Typical frequencies of physiological tremor are in the range of 1 Hz up to 20 Hz, wherein the amplitudes are usually higher al lower frequencies leading to blurring of images captured.
There are two different approaches to optical image stabilization possible. A first approach is to move a single or multiple optical elements over a fixed sensor plate in order to offset the effect of the changing field of view due to hand shaking. A second approach is to move the optical sensor in response to the movement of the camera.
The second approach appears to yield the most promising results. It is a challenge for the designers of image stabilization systems to keep any dust from the moving optical sensor plate, to consider the issue of electrical connections between the moving optical sensor and to the fixed part of the camera, to minimize the reduction of the usable area of the moving optical sensor, and to minimize the impact of the movable optical sensor upon the size of a camera module.
Solutions dealing with image stabilization of cameras are described in the following patents:
U.S. Patent Application Publication (US 2007/0236577 to Ke et al.) teaches a system and method providing image stabilization in an image capture device. In one embodiment, a system includes a stationary base included in an image capture device. The system may also include a movable base positioned on top of the stationary base. A point contactor including a set of ball bearings is configured to be either connected to the stationary base such that the set of ball bearings contact a supporting module connected to the movable base such that the movable base moves in relation to the stationary base, or connected to the movable base such that the set of ball bearings contact a supporting module connected to the stationary base such that the movable base moves in relation to the stationary base.
U.S. Patent Application Publication (US 2007/0172220 to Masuda) discloses an image stabilization apparatus, which can provide enhanced accuracy of image stabilization. The apparatus includes a movable member movable relative to a fixed member of the apparatus, plural flexible members which movably support the movable member at least in a direction orthogonal to the optical axis, a portion of each of the flexible members on one end side in a direction along the optical axis being fixed to the fixed member, a portion of each of the flexible members on the other end side being fixed to the movable member, and an actuator which drives the movable member. The flexural rigidity of at least one of the plural flexible members in the direction orthogonal to the optical axis is different from that of the other at least one flexible member in that direction so as to suppress rotation of the movable member driven by the actuator.
U.S. Patent Application Publication (US 2008/0260368 to Chang) discloses an image stabilization apparatus for stabilizing an image sensor. The image stabilization apparatus includes a transmission component whereon a slot is formed. The image stabilization apparatus further includes a rotary motor including an annular rotor connected to the transmission component, and an annular stator disposed on a side of the annular rotor. The annular rotor is capable of rotating relative to the annular stator. The image stabilization apparatus further includes a carrier for carrying the image sensor. The carrier includes a shaft disposed inside the slot in a slidable manner. The image stabilization apparatus further includes a linear motor coupled to the transmission component and the shaft of the carrier for driving the carrier to slide inside the slot.